In this work, the recent achievements in the application of solid oxides fuel cells (SOFCs) are discussed. This paper summarizes the progress in two major topics: the materials for the electrolytes, anode, and cathode, and the fuels used, such as hydrocarbon, alcohol, and solid carbon fuels. Various aspects related to the development of new materials for the main components of the materials for electrocatalysts and for solid electrolytes (e.g., pure metals, metal alloys, high entropy oxides, cermets, perovskite oxides, Ruddlesden–Popper phase materials, scandia-stabilized-zirconia, perovskite oxides, and ceria-based solid electrolytes) are reported in a coherent and explanatory way. The selection of appropriate material for electrocatalysts and for solid electrolyte is crucial to achieve successful commercialization of the SOFC technology, since enhanced efficiency and increased life span is desirable. Based on the recent advancements, tests were conducted in a biogas-fueled Ni-YSZ/YSZ/GDC/LSC commercial cell, to elucidate the suitability of the LSC as an anode. Results obtained encourage the application of LSC as an anode in actual SOFC and SOFEC systems. Thus, H₂-SOFC demonstrated a satisfying ASR value, while, for biogas-assisted electrolysis, the current values slightly increased compared to the methane-SOFEC, and for a 50/50 biogas mixture of methane and carbon dioxide, the corresponding value presented the higher increase.

Based upon the thermodynamic simulation of a biogas-SOFC integrated process and the costing of its elements, the present work examines the economic feasibility of biogas-SOFCs for combined heat and power (CHP) generation, by the comparison of their economic performance against the conventional biogas-CHP with internal combustion engines (ICEs), under the same assumptions. As well as the issues of process scale and an SOFC’s cost, examined in the literature, the study brings up the determinative effects of: (i) the employed SOFC size, with respect to its operational point, as well as (ii) the feasibility criterion, on the feasibility assessment. Two plant capacities were examined (250 m³·h⁻¹ and 750 m³·h⁻¹ biogas production), and their feasibilities were assessed by the Internal Rate of Return (IRR), the Net Present Value (NPV) and the Pay Back Time (PBT) criteria. For SOFC costs at 1100 and 2000 EUR·kW_el⁻¹, foreseen in 2035 and 2030, respectively, SOFCs were found to increase investment (by 2.5–4.5 times, depending upon a plant’s capacity and the SOFC’s size) and power generation (by 13–57%, depending upon the SOFC’s size), the latter increasing revenues. SOFC-CHP exhibits considerably lower IRRs (5.3–13.4% for the small and 16.8–25.3% for the larger plant), compared to ICE-CHP (34.4%). Nonetheless, according to NPV that does not evaluate profitability as a return on investment, small scale biogas-SOFCs (NPV_max: EUR 3.07 M) can compete with biogas-ICE (NPV: EUR 3.42 M), for SOFCs sized to operate at 70% of the maximum power density (MPD) and with a SOFC cost of 1100 EUR·kW_el⁻¹, whereas for larger plants, SOFC-CHP can lead to considerably higher NPVs (EUR 12.5–21.0 M) compared to biogas-ICE (EUR 9.3 M). Nonetheless, PBTs are higher for SOFC-CHP (7.7–11.1 yr and 4.2–5.7 yr for the small and the large plant, respectively, compared to 2.3 yr and 3.1 yr for biogas-ICE) because the criterion suppresses the effect of SOFC-CHP-increased revenues to a time period shorter than the plant’s lifetime. Finally, the economics of SOFC-CHP are optimized for SOFCs sized to operate at 70–82.5% of their MPD, depending upon the SOFC cost and the feasibility criterion. Overall, the choice of the feasibility criterion and the size of the employed SOFC can drastically affect the economic evaluation of SOFC-CHP, whereas the feasibility criterion also determines the economically optimum size of the employed SOFC.

The present work conducts a preliminary techno-economic feasibility study for a single municipal solid waste mass burning to an electricity plant for the total municipal solid waste potential of the Region of Eastern Macedonia – Thrace, in Greece. For a certain applied and highly efficient technology and an installed capacity of 400,000 t of municipal solid waste per year, the available electrical power to grid would be approximately 260 GWh per year (overall plant efficiency 20.5% of the lower heating value). The investment for such a plant was estimated at €200m. Taking into account that 37.9% of the municipal solid waste lower heating value can be attributed to their renewable fractions, and Greek Law 3851/2010, which transposes Directive 2009/28/EC for Renewable Energy Sources, the price of the generated electricity was calculated at €53.19/MWh_e. Under these conditions, the economic feasibility of such an investment depends crucially on the imposed gate fees. Thus, in the gate fee range of 50–110 € t⁻¹, the internal rate of return increases from 5% to above 15%, whereas the corresponding pay-out time periods decrease from 11 to about 4 years.

The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO₂ gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at 500 °C (LG500), and carbonization at 800 °C (LG800). Physicochemical characterization studies, including proximate and ultimate analysis, X-ray Diffraction (XRD), and Raman spectroscopy, revealed that the thermal treatment under inert atmospheres leads to chars with increased fixed carbon content and less ordered surface structures. The CO₂ gasification reactivity of pristine LG and as-produced chars was examined by thermogravimetric (TG) analysis and in batch mode gasification tests under both isothermal and non-isothermal conditions. The key parameters affecting the devolatilization and gasification steps in the overall process toward CO-rich gas mixtures were thoroughly explored. The gasification performance of the examined fuels in terms of carbon conversion, instant CO production rate, and syngas generation revealed an opposite reactivity order during each stage. TG analysis demonstrated that raw lignite (LG) was more reactive during the thermal devolatilization phase at low and intermediate temperatures (da/dt_max,devol. = 0.022 min⁻¹). By contrast, LG800 exhibited superior gasification reactivity at high temperatures (da/dt_max,gas. = 0.1 min⁻¹). The latter is additionally corroborated by the enhanced CO formation of LG800 samples under both non-isothermal (5.2 mmol) and isothermal (28 mmol) conditions, compared to 4.1 mmol and 13.8 mmol over the LG sample, respectively. The pronounced CO₂ gasification performance of LG800 was attributed to its higher fixed carbon content and disordered surface structure compared to LG, LG300, and LG500 samples.

The aim of this study is to provide a comprehensive analysis of the outcome of two separate techno-economic studies that were conducted for the scaled-up and industrially relevant processes of a) synthetic natural gas (SNG) production from captured (cement-based) CO₂ and green-H₂ (via renewable-assisted electrolysis) and b) combined electricity and crude biofuel production through the integration of biomass pyrolysis, gasification, and solid oxide fuel cells. As was found, the SNG production process seems more feasible from an economic perspective as it can be comparable to current market values.